The present invention relates to a prosthetic implant device, and more particularly to such implants which include a bearing insert or articulation member attached to a base support or reinforcing member. This invention is particularly suitable for use as a tibial component of a knee implant prosthesis, although is not limited thereto.
Heretofore, numerous ways have been utilized to secure an articulating bearing insert to a base support. One such example is U.S. Pat. No. 4,501,031 to McDaniel et al. which discloses a means of molding the articulating surface onto the base support to permanently secure this surface to the base support. Alternatively, it is noted that bearing inserts may be removably attached to a base support as shown in various ways by the following documents. U.S. Pat. No. 3,958,278 to Lee et al. discloses a tibial component which includes a removable E-shaped portion 25 on the base support which enables insertion or removal of the bearing insert 29. U.S. Pat. No. 4,016,606 to Murray et al. discloses a bearing insert which slides into a base support and is then secured by a locking pin inserted through both the insert and support. U.S. Pat. No. 4,207,627 to Cloutier discloses a replaceable bearing insert which has a lip which interlocks with a recess in the base support. U.S. Pat. No. 4,257,129 to Volz discloses a bearing insert which is slidably received onto a base support and then secured by a removable horizontal clip disposed about a removable vertical pin. U.S. Pat. No. 4,470,158 to Pappas et al. discloses a circular snap-ring (see FIGS. 10, 3-5 and 7-9) to unit prosthetic components. Groove 25 in component 11 retains snap-ring 24 when nonmetallic bearing insert 12 is positioned within component 11. The insert 12 can be removed by spreading the ears 23 apart through aperture 22 in component 11. It is noted that the single snap-ring 24 and corresponding grooves substantially fully encircle or surround the components which have circular attachment configurations. European Pat. No. EP 0 032 828 A2 to Lindstrand et al. discloses a bearing portion which is deformable to provide a releasable snap fit connection to the base support.